U.S. patent application number 13/286717 was filed with the patent office on 2013-05-02 for system and method for diagnosing faults in an oxygen sensor.
This patent application is currently assigned to GM Global Technology Operations LLC. The applicant listed for this patent is Michael John Dokter, Scott Jeffrey, Stephen Paul Levijoki, Thomas J. Majcher, John W. Siekkinen. Invention is credited to Michael John Dokter, Scott Jeffrey, Stephen Paul Levijoki, Thomas J. Majcher, John W. Siekkinen.
Application Number | 20130104626 13/286717 |
Document ID | / |
Family ID | 48084611 |
Filed Date | 2013-05-02 |
United States Patent
Application |
20130104626 |
Kind Code |
A1 |
Levijoki; Stephen Paul ; et
al. |
May 2, 2013 |
SYSTEM AND METHOD FOR DIAGNOSING FAULTS IN AN OXYGEN SENSOR
Abstract
A system according to the principles of the present disclosure
includes an error period module and a sensor diagnostic module. The
error period module determines an error period based on an amount
of time that a first air/fuel ratio and a desired air/fuel ratio
are different. A first oxygen sensor generates a first signal
indicating the first air/fuel ratio. The sensor diagnostic module
diagnoses a fault in the first oxygen sensor when the error period
is greater than a predetermined period.
Inventors: |
Levijoki; Stephen Paul;
(Swartz Creek, MI) ; Majcher; Thomas J.; (Orchard
Lake, MI) ; Siekkinen; John W.; (Novi, MI) ;
Dokter; Michael John; (Okemos, MI) ; Jeffrey;
Scott; (Hartland, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Levijoki; Stephen Paul
Majcher; Thomas J.
Siekkinen; John W.
Dokter; Michael John
Jeffrey; Scott |
Swartz Creek
Orchard Lake
Novi
Okemos
Hartland |
MI
MI
MI
MI
MI |
US
US
US
US
US |
|
|
Assignee: |
GM Global Technology Operations
LLC
Detroit
MI
|
Family ID: |
48084611 |
Appl. No.: |
13/286717 |
Filed: |
November 1, 2011 |
Current U.S.
Class: |
73/23.32 |
Current CPC
Class: |
F02D 41/1456 20130101;
F02D 41/1495 20130101; F02D 41/1454 20130101 |
Class at
Publication: |
73/23.32 |
International
Class: |
G01M 15/10 20060101
G01M015/10 |
Claims
1. A system comprising: an error period module that determines an
error period based on an amount of time that a first air/fuel ratio
and a desired air/fuel ratio are different, wherein a first oxygen
sensor generates a first signal indicating the first air/fuel
ratio; and a sensor diagnostic module that diagnoses a fault in the
first oxygen sensor when the error period is greater than a
predetermined period.
2. The system of claim 1, wherein the error period module increases
the error period when the first air/fuel ratio is rich and the
desired air/fuel ratio is lean.
3. The system of claim 1, wherein the error period module increases
the error period when the first air/fuel ratio is lean and the
desired air/fuel ratio is rich.
4. The system of claim 1, wherein the error period module sets the
error period to zero when the first air/fuel ratio and the desired
air/fuel ratio are both one of rich and lean.
5. The system of claim 1, wherein the first oxygen sensor is a
narrowband sensor.
6. The system of claim 1, wherein the first oxygen sensor is a
wideband sensor.
7. The system of claim 1, further comprising a fuel control module
that controls fuel delivery to an engine independent from the first
air/fuel ratio when the fault is diagnosed.
8. The system of claim 7, wherein the fuel control module controls
fuel delivery to the engine based on an engine operating condition
that is not determined based on input received from an oxygen
sensor.
9. The system of claim 7, wherein the fuel control module controls
fuel delivery to the engine based on a second air/fuel ratio when
the fault is diagnosed, wherein a second oxygen sensor generates a
second signal indicating the second air/fuel ratio.
10. The system of claim 9, wherein the first oxygen sensor is
disposed downstream from a first set of cylinders, the second
oxygen sensor is disposed downstream from a second set of
cylinders, and the fuel control module controls fuel delivery to
the first set and the second set based on the second air/fuel ratio
when the fault is diagnosed.
11. A method comprising: determining an error period based on an
amount of time that a first air/fuel ratio and a desired air/fuel
ratio are different, wherein a first oxygen sensor generates a
first signal indicating the first air/fuel ratio; and diagnosing a
fault in the first oxygen sensor when the error period is greater
than a predetermined period.
12. The method of claim 11, further comprising increasing the error
period when the first air/fuel ratio is rich and the desired
air/fuel ratio is lean.
13. The method of claim 11, further comprising increasing the error
period when the first air/fuel ratio is lean and the desired
air/fuel ratio is rich.
14. The method of claim 11, further comprising setting the error
period to zero when the first air/fuel ratio and the desired
air/fuel ratio are both one of rich and lean.
15. The method of claim 11, wherein the first oxygen sensor is a
narrowband sensor.
16. The method of claim 11, wherein the first oxygen sensor is a
wideband sensor.
17. The method of claim 11, further comprising controlling fuel
delivery to an engine independent from the first air/fuel ratio
when the fault is diagnosed.
18. The method of claim 17, further comprising controlling fuel
delivery to the engine based on an engine operating condition that
is not determined based on input received from an oxygen
sensor.
19. The method of claim 17, further comprising controlling fuel
delivery to the engine based on a second air/fuel ratio when the
fault is diagnosed, wherein a second oxygen sensor generates a
second signal indicating the second air/fuel ratio.
20. The method of claim 19, further comprising controlling fuel
delivery to a first set of cylinders and a second set of cylinders
based on the second air/fuel ratio when the fault is diagnosed,
wherein the first oxygen sensor is disposed downstream from the
first set and the second oxygen sensor is disposed downstream from
the second set.
Description
FIELD
[0001] The present disclosure relates to systems and methods for
diagnosing faults in an oxygen sensor disposed in an exhaust system
of an engine.
BACKGROUND
[0002] The background description provided herein is for the
purpose of generally presenting the context of the disclosure. Work
of the presently named inventors, to the extent it is described in
this background section, as well as aspects of the description that
may not otherwise qualify as prior art at the time of filing, are
neither expressly nor impliedly admitted as prior art against the
present disclosure.
[0003] An oxygen sensor may be positioned in an exhaust system of
an engine. The oxygen sensor may generate an oxygen signal
indicating oxygen levels in exhaust gas from the engine. The oxygen
signal may also indicate an air/fuel ratio of the engine, which may
be referred to as an actual air/fuel ratio. The amount of air and
fuel provided to cylinders of the engine may be controlled based on
a desired air/fuel ratio, such as a stoichiometric air/fuel ratio,
and/or the actual air/fuel ratio.
[0004] Fuel control systems may operate in a closed-loop state or
an open-loop state. In the closed-loop state, fuel delivery may be
controlled to minimize differences between the desired air/fuel
ratio and the actual air/fuel ratio. In the open-loop state, fuel
delivery may be controlled independent from the actual air/fuel
ratio. For example, fuel delivery may be controlled based on a fuel
map.
SUMMARY
[0005] A system according to the principles of the present
disclosure includes an error period module and a sensor diagnostic
module. The error period module determines an error period based on
an amount of time that a first air/fuel ratio and a desired
air/fuel ratio are different. A first oxygen sensor generates a
first signal indicating the first air/fuel ratio. The sensor
diagnostic module diagnoses a fault in the first oxygen sensor when
the error period is greater than a predetermined period.
[0006] Further areas of applicability of the present disclosure
will become apparent from the detailed description provided
hereinafter. It should be understood that the detailed description
and specific examples are intended for purposes of illustration
only and are not intended to limit the scope of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The present disclosure will become more fully understood
from the detailed description and the accompanying drawings,
wherein:
[0008] FIG. 1 is a functional block diagram of an example engine
system according to the principles of the present disclosure;
[0009] FIG. 2 is a functional block diagram of an example control
system according to the principles of the present disclosure;
[0010] FIG. 3 is a flowchart illustrating an example control method
according to the principles of the present disclosure; and
[0011] FIG. 4 is a graph illustrating example control signals
according to the principles of the present disclosure.
DETAILED DESCRIPTION
[0012] An oxygen sensor may be a narrowband sensor or a wideband
sensor. A narrowband sensor outputs a voltage indicating whether an
air/fuel ratio is rich or lean. For example, an output voltage
greater than 450 millivolts (mV) may indicate a rich air/fuel
ratio, and an output voltage less than 450 mV may indicate a lean
air/fuel ratio. A wideband sensor outputs a voltage indicating the
value of the air/fuel ratio.
[0013] A bias circuit may cause the oxygen sensor to output a
voltage indicating that the air/fuel ratio is rich or lean in the
event of an open circuit or a short circuit. For example, an oxygen
sensor may normally output a voltage between 50 mV and 850 mV, and
the oxygen sensor may output a voltage of 1900 mV when biased.
Thus, the oxygen sensor may be stuck in a rich or lean state due to
the bias circuit. A sensor that is stuck in a rich or lean state
may cause rough engine operation and/or engine stalls.
[0014] A system and method according to the principles of the
present disclosure diagnoses a fault in an oxygen sensor based on
an error period. The error period is the amount of time that a
desired air/fuel ratio and an actual air/fuel ratio are different.
The actual air/fuel ratio is indicated by a signal generated by the
oxygen sensor. The error period may be increased when the desired
air/fuel ratio is lean and the actual air/fuel ratio is rich. The
error period may also be increased when the desired air/fuel ratio
is rich and the actual air/fuel ratio is lean. A fault in the
oxygen sensor may be diagnosed when the error period is greater
than a predetermined period.
[0015] A system and method according to the principles of the
present disclosure may operate in an open-loop state or a
pseudo-open-loop state when a faulty oxygen sensor is diagnosed. In
the open-loop state, fuel delivery may be controlled based on
engine operating conditions that are not determined based on input
received from an oxygen sensor. In the pseudo-open-loop state, fuel
delivery may be controlled based on input received from an oxygen
sensor that is not faulty. The open-loop state may be employed when
a single oxygen sensor is disposed downstream from an engine (e.g.,
a single bank engine). The pseudo-open-loop state may be employed
when two or more oxygen sensors are disposed downstream from an
engine (e.g., a dual bank engine).
[0016] Diagnosing a fault in an oxygen sensor based on the error
period provides diagnostic information that may be retrieved and
utilized when a vehicle is serviced. Controlling fuel delivery in
the open-loop state or the pseudo-open-loop state when a faulty
oxygen sensor is diagnosed prevents rough engine operation and
engine stalls. Preventing rough engine operation and engine stalls
improves customer satisfaction.
[0017] Referring to FIG. 1, an engine system 10 includes an engine
12 that combusts an air/fuel mixture to produce drive torque for a
vehicle. Air is drawn into the engine 12 through an intake system
14. The intake system 14 includes a throttle valve 16 and an intake
manifold 18. The throttle valve 16 may include a butterfly valve
having a rotatable blade. The throttle valve 16 opens to draw air
into the intake manifold 18. An engine control module (ECM) 20
outputs a throttle control signal 22 to control the amount of air
drawn into the intake manifold 18.
[0018] Air from the intake manifold 18 is drawn into cylinders 24
of the engine 12 through an intake valve 26. Although the engine 12
is depicting as having eight cylinders, the engine 12 may have more
or less cylinders. The engine 12 may be a dual bank engine, and the
cylinders 24 may be distributed between a first bank 28 and a
second bank 30. Alternatively, the engine 12 may be a single bank
engine.
[0019] One or more fuel injectors 32 inject fuel into the engine
12. Fuel may be injected into the intake manifold 18 at a central
location or at multiple locations, such as near the intake valve 26
of each of the cylinders 24. In various implementations, fuel may
be injected directly into the cylinders 24 or into mixing chambers
associated with the cylinders 24. The ECM 20 outputs a fuel control
signal 34 to control the amount of fuel injected by the fuel
injectors 32.
[0020] The injected fuel mixes with air and creates an air/fuel
mixture in the cylinders 24. Pistons (not shown) within the
cylinders 24 compress the air/fuel mixture. The engine 12 may be a
compression-ignition engine, in which case compression in the
cylinders 24 ignites the air/fuel mixture. Alternatively, the
engine 12 may be a spark-ignition engine, in which case spark plugs
(not shown) in the cylinder 24 generate a spark that ignites the
air/fuel mixture. The ECM 20 may output a spark control signal (not
shown) to control when the spark plugs generate a spark (i.e.,
spark timing).
[0021] The byproducts of combustion are expelled through an exhaust
valve 36 and exhausted from the vehicle through an exhaust system
38. The exhaust system 38 includes an exhaust manifold 40 and a
three-way catalyst (TWC) 42. The TWC 42 reduces nitrogen oxide and
oxidizes carbon monoxide and hydrocarbon. The TWC 42 may store
oxygen when an air/fuel ratio of the engine 12 is lean, and oxygen
stored in the TWC 42 may be consumed as carbon monoxide and
hydrocarbon are oxidized when the air/fuel ratio is rich. The ECM
20 may oscillate the air/fuel ratio between rich and lean within a
narrow band near a stoichiometric air/fuel ratio to minimize
emissions.
[0022] An intake air temperature (IAT) sensor 44 measures the
temperature of air drawn through the intake system 14 and generates
an IAT signal 46 indicating the intake air temperature. A mass
airflow (MAF) sensor 48 measures the mass flow rate of air drawn
through the intake system and generates a MAF signal 50 indicating
the mass airflow. A manifold absolute pressure (MAP) sensor 52
measures pressure in the intake manifold 18 and generates a MAP
signal 54 indicating the manifold pressure. A crankshaft position
(CPS) sensor 56 measures the position of the crankshaft and
generates a CPS signal 58 indicating the position of the crankshaft
(and engine speed).
[0023] A first oxygen (O2) sensor 60 measures a first oxygen level
in exhaust gas from the first bank 28 and generates a first O2
signal 62 indicating the first oxygen level. A second O2 sensor 64
measures a second oxygen level in exhaust gas from the second bank
30 and generates a second O2 signal 66 indicating the second oxygen
level. An exhaust gas temperature (EGT) sensor 68 measures the
temperature of exhaust gas and generates an EGT signal 70
indicating the exhaust gas temperature. A third O2 sensor 72
measures a third oxygen level in exhaust gas downstream from the
TWC 42 and generates a third O2 signal 74 indicating the third
oxygen level. The oxygen sensors 60, 64, 72 may be narrowband
sensors or wideband sensors.
[0024] The ECM 20 receives the signals generated by the sensors
discussed above and controls the engine 12 based on the signals
received. The ECM 20 may diagnose a fault in the first O2 sensor 60
and/or the second O2 sensor 64. Although the ECM 20 may diagnose a
fault in either of the oxygen sensors 60, 64, for simplicity, the
discussion below describes the ECM 20 diagnosing a fault in the
first O2 sensor 60. The ECM 20 may diagnose a fault in the second
O2 sensor 64 in a similar manner.
[0025] The ECM 20 diagnoses a fault in the first O2 sensor 60 based
on an error period. The error period is the amount of time that a
desired air/fuel ratio and an actual air/fuel ratio are different.
The ECM 20 adjusts the fuel control signal 34 to achieve the
desired air/fuel ratio. The ECM 20 determines the actual air/fuel
ratio based on the first O2 signal 62.
[0026] The ECM 20 may increase the error period when the desired
air/fuel ratio is lean and the actual air/fuel ratio is rich. The
ECM 20 may increase the error period when the desired air/fuel
ratio is rich and the actual air/fuel ratio is lean. The ECM 20 may
diagnose a fault in the first O2 sensor 60 when the error period is
greater than a predetermined period.
[0027] Referring to FIG. 2, an example implementation of the ECM 20
includes an air/fuel ratio module 202, an error period module 204,
a sensor diagnostic module 206, a fuel control module 208, and a
throttle control module 210. The air/fuel ratio module 202
determines whether an actual air/fuel ratio is rich or lean based
on the first O2signal 62. For example, the actual air/fuel ratio
may be rich when the first O2 signal 62 is greater than a
predetermined voltage (e.g., 450 mV) and the actual air/fuel ratio
may be lean when the first O2 signal 62 is less than the
predetermined voltage. The predetermined voltage may correspond to
a stoichiometric air/fuel ratio. The air/fuel ratio module 202
outputs a signal indicating whether the actual air/fuel ratio is
rich or lean.
[0028] The air/fuel ratio module 202 may determine the value of the
actual air/fuel ratio based on the first O2 signal 62 and/or the
type of fuel combusted by the engine 12. For example, the air/fuel
ratio module 202 may determine that the actual air/fuel ratio is
14.7 when the first O2 signal 62 is equal to the predetermined
voltage and the fuel type is gasoline. The fuel type may be
predetermined and/or provided to the air/fuel ratio module 202
using, for example, an instrument panel and/or a service tool. The
air/fuel ratio module 202 may output the value of the actual
air/fuel ratio.
[0029] The error period module 204 determines an error period based
on the actual air/fuel ratio and a desired air/fuel ratio. The
error period is the amount of time that the actual air/fuel ratio
and the desired air/fuel ratio are different. The desired air/fuel
ratio may be a predetermined ratio such as a stoichiometric ratio.
Alternatively, the fuel control module 208 may determine the
desired air/fuel ratio, as discussed below, and output the desired
air/fuel ratio to the error period module 204.
[0030] The error period module 204 may increase a rich error period
when the desired air/fuel ratio is lean and the actual air/fuel
ratio is rich. The error period module 204 may increase a lean
error period when the desired air/fuel ratio is rich and the actual
air/fuel ratio is lean. The error period module 204 may set the
error period to zero when the desired air/fuel ratio and the actual
air/fuel ratio are either rich or lean. The error period module 204
outputs the error periods.
[0031] The sensor diagnostic module 206 diagnoses a fault in the
first O2 sensor 60 based on an error period. The sensor diagnostic
module 206 may diagnose a stuck rich fault when the rich error
period is greater than a predetermined period (e.g., 3 seconds).
The sensor diagnostic module 206 may diagnose a stuck lean fault
when the lean error period is greater than the predetermined
period. The sensor diagnostic module 206 outputs a signal
indicating when a fault in the first O2 sensor 60 is diagnosed. The
sensor diagnostic module 206 may also set a diagnostic trouble code
and/or activate a service indicator such as a visible message when
a fault in the first O2 sensor 60 is diagnosed.
[0032] The sensor diagnostic module 206 may refrain from diagnosing
a fault in the first O2 sensor 60 when the first O2 signal 62 and
the third O2 signal 74 indicate a lean air/fuel ratio or when the
first O2 signal 62 and the third O2 signal 74 indicate a rich
air/fuel ratio. The sensor diagnostic module 206 may diagnose the
stuck lean fault when the lean error period is greater than the
predetermined period and the third O2 signal 74 indicates a rich
air/fuel ratio. The sensor diagnostic module 206 may diagnose the
stuck rich fault when the rich error period is greater than the
predetermined period and the third O2 signal 74 indicates a lean
air/fuel ratio.
[0033] The fuel control module 208 outputs the fuel control signal
34 to control the amount of fuel (i.e., the fuel mass) injected by
the fuel injectors 32. The fuel control module 208 may control the
fuel mass based on the amount of air (i.e., the air mass) drawn
into the intake manifold 18 to achieve the desired air/fuel ratio.
The throttle control module 210 may determine the air mass, as
discussed below, and output the air mass to the fuel control module
208. The fuel control module 208 may determine the desired air/fuel
ratio based on engine operating conditions to minimize emissions.
The engine operating conditions may include the intake air
temperature, the mass airflow, the manifold pressure, the engine
speed, and/or the exhaust gas temperature.
[0034] The fuel control module 208 may operate in a closed-loop
state when the first O2 sensor 60 is operating normally. In the
closed-loop state, the fuel control module 208 adjusts the fuel
mass to minimize differences between the desired air/fuel ratio and
the actual air/fuel ratio. The fuel control module 208 may control
fuel delivery to the first bank 28 based on input received from the
first O2 sensor 60 and control fuel delivery to the second bank 30
based on input received from the second O2 sensor 64.
[0035] Alternatively, the first O2 sensor 60 may be downstream from
the first bank 28 and the second bank 30, and the fuel control
module 208 may control fuel delivery to the first bank 28 and the
second bank 30 based on input received from first O2 sensor 60.
[0036] The fuel control module 208 may operate in an open-loop
state or a pseudo-open-loop state when a fault is diagnosed in the
first O2 sensor 60. The fuel control module 208 may operate in the
pseudo-open-loop state when more than one O2 sensor is disposed
downstream from the engine 12 and one of the O2 sensors is not
faulty. The fuel control module 208 may operate in the open-loop
state when only a faulty O2 sensor is disposed downstream from the
engine 12.
[0037] In the open-loop state, the fuel control module 208 may
control fuel delivery independent from input received from the
first O2 sensor 60. For example, the fuel control module 208 may
control fuel delivery based on a fuel map. The fuel map may specify
fuel delivery parameters (e.g., fuel mass, fueling rate) based on
engine operating conditions. The engine operating conditions may
include the intake air temperature, the mass airflow, the manifold
pressure, the engine speed, and/or the exhaust gas temperature.
[0038] In the pseudo-open-loop state, when a fault is diagnosed in
the first O2 sensor 60, the fuel control module 208 may control
fuel delivery to the first bank 28 and the second bank 30 based on
input received from the second O2 sensor 64. For example, the fuel
control module 208 may control fuel delivery to the first bank 28
and the second bank 30 to minimize differences between an actual
air/fuel ratio and the desired air/fuel ratio. The air/fuel ratio
module 202 may determine the actual air/fuel ratio based on the
second O2 signal 66. Conversely, when a fault is diagnosed in the
second O2 sensor 64, the fuel control module 208 may control fuel
delivery to the first bank 28 and the second bank 30 based on input
received from the first O2 sensor 60.
[0039] The throttle control module 210 outputs the throttle control
signal 22 to control the amount of air (i.e., the air mass) drawn
into the intake manifold 18. The throttle control module 210 may
adjust the air mass to minimize differences between a desired air
mass and an actual air mass. The throttle control module 210 may
determine the desired air mass based on driver input. For example,
the driver input may be generated based on an accelerator pedal
position and/or a cruise control setting.
[0040] The throttle control module 210 may determine the actual air
mass based on engine operating conditions. The engine operating
conditions may include the intake air temperature, the mass
airflow, and/or the manifold pressure. The engine operating
conditions may also include a throttle position. The throttle
position may be measured and/or determined based on the throttle
control signal 22. The throttle control module 210 may adjust the
throttle position to minimize differences between a desired
throttle position and an actual throttle position. The throttle
control module 210 may determine the desired throttle position
based on the driver input and output the resulting air mass.
[0041] Referring to FIG. 3, a method for diagnosing a fault in an
oxygen sensor begins at 302. The oxygen sensor may be a narrowband
sensor or a wideband sensor. At 304, the method determines whether
a desired air/fuel ratio is lean. If 304 is true, the method
continues at 306. Otherwise, the method continues at 308.
[0042] The desired air/fuel ratio may be a predetermined ratio such
a stoichiometric ratio or a ratio that oscillates between rich and
lean within a predetermined range. The method may determine the
desired air/fuel ratio based on engine operating conditions.
[0043] The engine operating conditions may include intake air
temperature, mass airflow, manifold pressure, engine speed, and/or
exhaust gas temperature.
[0044] At 306, the method determines whether an actual air/fuel
ratio is rich. If 306 is true, the method continues at 310.
Otherwise, the method continues at 312. The method determines
whether the actual air/fuel ratio is rich or lean based on output
voltage of the oxygen sensor. For example, the actual air/fuel
ratio may be rich when the output voltage is greater than 450
millivolts (mV), and the actual air/fuel ratio may be lean when the
output voltage is less than 450 millivolts.
[0045] At 310, the method increases a rich error period. At 314,
the method determines whether the rich error period is greater than
a predetermined period (e.g., 3 seconds). If 314 is true, the
method continues at 316. Otherwise, the method continues at 304. At
316, the method diagnoses a stuck rich fault in the oxygen sensor.
The method may set a diagnostic trouble code and/or activate a
service indicator such as a visible message to indicate when the
stuck rich fault is diagnosed.
[0046] At 318, the method operates in an open-loop state or a
pseudo-open-loop state. In the open-loop state, the method controls
fuel delivery independent from input received from an oxygen
sensor. In the pseudo-open-loop state, the method controls fuel
delivery based on input received from an oxygen sensor that is not
faulty.
[0047] At 308, the method determines whether the actual air/fuel
ratio is rich. If 308 is true, the method continues at 312.
Otherwise, the method continues at 320. At 320, the method
increases a lean error period. At 312, the method sets an error
period to zero. The method may set the rich error period to zero
and/or set the lean error period to zero.
[0048] At 322, the method determines whether the lean error period
is greater than the predetermined period. If 322 is true, the
method continues at 324. Otherwise, the method continues at 304. At
324, the method diagnoses a stuck lean fault in the oxygen sensor.
The method may set a diagnostic trouble code and/or activate a
service indicator such as a visible message to indicate when the
stuck lean fault is diagnosed.
[0049] Referring now to FIG. 4, an x-axis 402 represents a first
sample count, a y-axis 404 represents voltage in millivolts (mV),
and a y-axis 406 represents a second sample count. The first sample
count and the second sample count indicate periods. The periods may
be determined based on the sampling rates of the first sample count
and the second sample count. The sampling rate of the first sample
count is 250 milliseconds (ms), and the sampling rate of the second
sample count is 100 ms.
[0050] An actual voltage 408 output by an oxygen sensor is plotted
relative to the x-axis 402 and the y-axis 404. A desired state 410
of the oxygen sensor is plotted relative to the x-axis 402 and a
y-axis 411. A rich error period 412, a lean error period 414, and
an error correction voltage 416 are plotted relative to the x-axis
402 and the y-axis 406. The desired state 410 may be a lean state
418 or a rich state 420. Fuel delivery to an engine may be
controlled based on the desired state 410 and the error correction
416.
[0051] The rich error period 412 increases and the lean error
period 414 decreases when the actual voltage 408 is greater than a
predetermined voltage and the desired state 410 is the lean state
418. The predetermined voltage may be a voltage that corresponds to
a stoichiometric air/fuel ratio. The rich error period 412
decreases and the lean error period 414 increases when the actual
voltage 408 is less than the predetermined voltage and the desired
state 410 is the rich state 420. A stuck rich fault in the oxygen
sensor is diagnosed when the rich error period 412 equals 3 seconds
(i.e., product of 30 counts and 100 ms). Fuel delivery to the
engine may be controlled independent from the actual voltage 408
when the stuck rich fault is diagnosed. For example, fuel delivery
to the engine may be controlled based on input received from a
different oxygen sensor that is not faulty.
[0052] The foregoing description is merely illustrative in nature
and is in no way intended to limit the disclosure, its application,
or uses. The broad teachings of the disclosure can be implemented
in a variety of forms. Therefore, while this disclosure includes
particular examples, the true scope of the disclosure should not be
so limited since other modifications will become apparent upon a
study of the drawings, the specification, and the following claims.
For purposes of clarity, the same reference numbers will be used in
the drawings to identify similar elements. As used herein, the
phrase at least one of A, B, and C should be construed to mean a
logical (A or B or C), using a non-exclusive logical OR. It should
be understood that one or more steps within a method may be
executed in different order (or concurrently) without altering the
principles of the present disclosure.
[0053] As used herein, the term module may refer to, be part of, or
include an Application Specific Integrated Circuit (ASIC); an
electronic circuit; a combinational logic circuit; a field
programmable gate array (FPGA); a processor (shared, dedicated, or
group) that executes code; other suitable hardware components that
provide the described functionality; or a combination of some or
all of the above, such as in a system-on-chip. The term module may
include memory (shared, dedicated, or group) that stores code
executed by the processor.
[0054] The term code, as used above, may include software,
firmware, and/or microcode, and may refer to programs, routines,
functions, classes, and/or objects. The term shared, as used above,
means that some or all code from multiple modules may be executed
using a single (shared) processor. In addition, some or all code
from multiple modules may be stored by a single (shared) memory.
The term group, as used above, means that some or all code from a
single module may be executed using a group of processors. In
addition, some or all code from a single module may be stored using
a group of memories.
[0055] The apparatuses and methods described herein may be
implemented by one or more computer programs executed by one or
more processors. The computer programs include processor-executable
instructions that are stored on a non-transitory tangible computer
readable medium. The computer programs may also include stored
data. Non-limiting examples of the non-transitory tangible computer
readable medium are nonvolatile memory, magnetic storage, and
optical storage.
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